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# Testcontainers Kafka
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Testcontainers Kafka module provides container implementations for running Apache Kafka during integration testing. It supports multiple Kafka distributions including Apache Kafka, Confluent Platform, and legacy compatibility modes with embedded or external Zookeeper and modern KRaft mode for Zookeeper-free deployments.
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## Package Information
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- **Package Name**: org.testcontainers:kafka
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- **Package Type**: maven
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- **Language**: Java
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- **Installation**: 
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  Maven:
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  ```xml
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  <dependency>
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      <groupId>org.testcontainers</groupId>
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      <artifactId>kafka</artifactId>
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      <version>1.21.3</version>
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      <scope>test</scope>
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  </dependency>
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  ```
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  Gradle:
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  ```groovy
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  testImplementation 'org.testcontainers:kafka:1.21.3'
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  ```
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## Core Imports
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```java
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import org.testcontainers.kafka.KafkaContainer;
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import org.testcontainers.kafka.ConfluentKafkaContainer;
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import org.testcontainers.utility.DockerImageName;
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```
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For legacy support (deprecated):
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```java
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import org.testcontainers.containers.KafkaContainer;
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```
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## Basic Usage
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```java
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import org.testcontainers.kafka.KafkaContainer;
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import org.testcontainers.utility.DockerImageName;
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// Apache Kafka using modern container
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try (KafkaContainer kafka = new KafkaContainer("apache/kafka:3.8.0")) {
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    kafka.start();
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    String bootstrapServers = kafka.getBootstrapServers();
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    // Use bootstrapServers to configure your Kafka clients
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    // Example: "localhost:32768"
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}
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// Confluent Platform using modern container
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try (ConfluentKafkaContainer kafka = new ConfluentKafkaContainer("confluentinc/cp-kafka:7.4.0")) {
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    kafka.start();
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    String bootstrapServers = kafka.getBootstrapServers();
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}
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```
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## Architecture
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The Testcontainers Kafka module provides three main container implementations:
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- **Modern Apache Kafka Container**: `org.testcontainers.kafka.KafkaContainer` for apache/kafka and apache/kafka-native images with KRaft mode by default
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- **Modern Confluent Container**: `org.testcontainers.kafka.ConfluentKafkaContainer` for confluentinc/cp-kafka images (7.4.0+) with KRaft mode by default
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- **Legacy Container**: `org.testcontainers.containers.KafkaContainer` (deprecated) supporting embedded Zookeeper, external Zookeeper, and KRaft modes
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- **Shared Helper**: `org.testcontainers.kafka.KafkaHelper` providing common functionality and constants for modern containers
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## Capabilities
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### Apache Kafka Container
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Modern container implementation for Apache Kafka with KRaft mode and flexible listener configuration.
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```java { .api }
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public class KafkaContainer extends GenericContainer<KafkaContainer> {
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    public KafkaContainer(String imageName);
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    public KafkaContainer(DockerImageName dockerImageName);
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    public KafkaContainer withListener(String listener);
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    public KafkaContainer withListener(String listener, Supplier<String> advertisedListener);
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    public String getBootstrapServers();
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}
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```
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[Apache Kafka Container](./apache-kafka-container.md)
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### Confluent Kafka Container
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Modern container implementation for Confluent Platform with KRaft mode and flexible listener configuration.
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```java { .api }
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public class ConfluentKafkaContainer extends GenericContainer<ConfluentKafkaContainer> {
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    public ConfluentKafkaContainer(String imageName);
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    public ConfluentKafkaContainer(DockerImageName dockerImageName);
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    public ConfluentKafkaContainer withListener(String listener);
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    public ConfluentKafkaContainer withListener(String listener, Supplier<String> advertisedListener);
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    public String getBootstrapServers();
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}
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```
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[Confluent Kafka Container](./confluent-kafka-container.md)
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### Legacy Kafka Container (Deprecated)
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Legacy container implementation with Zookeeper and KRaft mode support. Use modern containers instead.
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```java { .api }
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@Deprecated
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public class KafkaContainer extends GenericContainer<KafkaContainer> {
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    public KafkaContainer(DockerImageName dockerImageName);
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    public KafkaContainer withEmbeddedZookeeper();
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    public KafkaContainer withExternalZookeeper(String connectString);
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    public KafkaContainer withKraft();
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    public KafkaContainer withClusterId(String clusterId);
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    public KafkaContainer withListener(Supplier<String> listenerSupplier);
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    public String getBootstrapServers();
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}
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```
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[Legacy Kafka Container](./legacy-kafka-container.md)
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### Kafka Helper
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Shared utility class providing common constants and functionality for modern Kafka containers.
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```java { .api }
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class KafkaHelper {
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    static final int KAFKA_PORT = 9092;
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    static final String STARTER_SCRIPT = "/tmp/testcontainers_start.sh";
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    static Map<String, String> envVars();
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}
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```
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[Kafka Helper](./kafka-helper.md)
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## Types
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### Docker Image Names
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```java { .api }
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// Apache Kafka images (for KafkaContainer)
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DockerImageName.parse("apache/kafka:3.8.0")
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DockerImageName.parse("apache/kafka-native:3.8.0")
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// Confluent Platform images (for ConfluentKafkaContainer)  
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DockerImageName.parse("confluentinc/cp-kafka:7.4.0")
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// Legacy support (deprecated KafkaContainer)
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DockerImageName.parse("confluentinc/cp-kafka:6.2.1")
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```
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### Listener Configuration
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```java { .api }
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// Simple listener format for modern containers
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String listener = "kafka:19092";
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// Supplier for dynamic advertised listeners
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Supplier<String> advertisedListener = () -> "external-host:9092";
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```
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### Common Container Methods
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All Kafka containers inherit standard Testcontainers functionality:
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```java { .api }
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// Container lifecycle
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public void start();
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public void stop();
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public boolean isRunning();
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// Network and port access
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public String getHost();
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public Integer getMappedPort(int originalPort);
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public KafkaContainer withNetwork(Network network);
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public KafkaContainer withNetworkAliases(String... aliases);
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// Environment and configuration
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public KafkaContainer withEnv(String key, String value);
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public KafkaContainer withEnv(Map<String, String> env);
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```
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### Constants
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```java { .api }
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// Modern containers (KafkaContainer, ConfluentKafkaContainer)
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static final int KAFKA_PORT = 9092;
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// Legacy container
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public static final int KAFKA_PORT = 9093;
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public static final int ZOOKEEPER_PORT = 2181;
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public static final String DEFAULT_CLUSTER_ID = "4L6g3nShT-eMCtK--X86sw";
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```